The present invention generally relates to network communications and, more specifically, to a method and system for providing improved circuit emulation service.
Circuit emulation service (CES) technique has been widely developed in the telecommunication industry for transport of channelized or unchannelized bandwidth over Asynchronous Transfer Mode (ATM) networks. Such technique is well known and is fully documented through industry standardization bodies such as ATM Forum and International Telecommunication Union (ITU-T). See, for example, “Circuit Emulation Service Interoperability Specification Ver. 2.0 (ATM Forum, January 1997)” and “B-ISDN ATM Adaptation Layer Specification: Type 1 AAL (ITU-T I.363.1, August 1996)”.
For structured CES, the standardized technique uses the “structured data transfer” method in AAL1 that employs a pointer to delineate the frame boundary. One or more octets within the AAL user information field of a frame can be assigned to a channel. Using a 8 KHz frame rate as an example, a channel with only one octet per frame would represent a 64 kbps circuit. A channel with 2 octets assigned per frame would represent a 128 kbps circuit and, in general, a channel with N octets per frame would be an N×64 kbps circuit.
The foregoing method works well in an environment where all channels have a common frame rate, for example, 8 KHz, for digitized voice in a time-division-multiplex (TDM) network. However, for equipment such as access aggregators that handle diverse traffic types and rates, it is difficult to achieve an optimal and uniform frame rate in such an environment. As a result, the standard CES technique cannot be used to transport all traffic between equipment due to the N×64 kbps (assuming a 8 KHz frame) restriction.
Hence, it would be desirable to develop a method and system that is capable of solving the foregoing problem, as well as others, by providing transport of channelized circuits of arbitrary bit rate.